This invention relates generally to flow measuring apparatus, and more particularly to a vortex-type flowmeter adapted to operate in conjunction with an external sensor coupled to a portable read-out device whereby the same sensor may be used to take readings from a large number of installed flowmeters.
After an oil well is drilled, oil may flow freely, producing up to a thousand barrels a day as a result of high reservoir pressure generated by natural gas trapped with the oil or the pressure of water layers above the oil. Ultimately, artificial lift expedients are required to increase oil recovery. One widely used form of secondary recovery is the waterflood technique wherein pressurized water is forced through an injection well adjacent the site of the producing well, the injected water flooding the oil bearing region and providing the necessary pressure for oil extraction.
In a secondary recovery system of this type, oil intermingled with water is yielded by the producing well. The water is thereafter separated from the oil and is returned to injection pumps delivering water to the injection well. These pumps supply pressurized water to several injection wells, so that the secondary recovery system involves a network of water lines leading to a group of functioning wells.
In maintaining and servicing a waterflood system, it is necessary to periodically check the water flow rate at various points in the water line network. The present practice is to effect measurement by means of turbine meters installed in the water lines. In the conventional turbine meter, the turbine rotor is mounted within the flow conduit, a permanent magnet being incorporated in the rotor. The rotating magnet induces an alternating-current in a pick-up coil located in the external housing of the meter, the freqency of the generated signal being proportional to the volumetric flow rate. The frequency of the signal is converted into a reading of flow rate.
Since turbine meters are relatively expensive, and a secondary oil recovery system requires a large number of such meters, one recent innovation has been to omit the pick-up coil from the meter and to provide a separate pick-up coil coupled to a battery-operated test set which affords a flow rate reading. This practice is feasible since it is only necessary for an operator to briefly check flow rate at the meter installation and then, if necessary, to make a manual valve adjustment to correct flow rate. Thus the operator who carries the pick-up coil and the test set makes a tour of the various turbine meter installations to check the flow rate.
The main drawback of turbine flowmeters in the context of a secondary oil recovery system is that because it has a rotor which is exposed to the water, there is a reliability problem in that the water being measured is often dirty and tends to foul and degrade the rotor and its bearings, particularly if the water contains abrasive particles and corrosive chemical constituents. Hence after prolonged use, the turbine meter may become inoperative or inaccurate.